These are brand new 6v connected in series. Im cycling them in the garage using a 3.5a light bulb load. I had an RvWhisper batt monitor installed and noticed it was reading super low at 12.05v. After poking around i found that if i touch my multimeter to the threaded post on the battery it will read 12.07v. But when i touch to the flat section on the same terminal it reads 12.4v. Adjusting the probe on the positive terminal doesnt matter. The heck is going no here?

I don't know about the connection, but your batteries are undercharged.

Bad thread to lead connection but if the lug is laying FLAT against a clean lead connector it should make no difference. Take that connection apart after taking a smartfone image of it.Now measure from same battery threaded post on pos to threaded post on neg. 6.3 volts? 4.2? Wiggle the threads while looking at voltage. If it even quivers you have a bad threads to lead post connection.Don't horse the stud or you will break it and a battery warranty will be denied.If the drama is not obviousSAND the ring lead ring around the stud and then SAND the ring on the lug around the cable eyelet ring terminal then reassemble. This is why I despise this type of connection.So what did you find?

Cool deal i will do some wiggling. The battery is not undercharged.

Full and after a rest a 12 volt deep cycle battery should show 12.7 volts...and a 6 volt 6.35.

Those threaded bolts are just stuck upside down in the lead top with a little lead around the bolt head. Like Mex said, the idea is to get your ring terminal lying on the flat lead part and use the bolt to tighten it down.You can overdo things and pull the bolt right out of its lead bed. Oops! Now what? BTDT. You can try those adapter gizmos that clamp to the lead post that have their own threaded bolts as your new connection point. EDIT--forgot to mention the low lead post on a 6 makes it difficult to attach the adapter clamp. You can drill holes in around the bottom and use screws down into the lead to hold it better. it works for a while, but gets loose. Just have to keep at it until it is time to get new batteries. BTDT. :(The resting voltage on your pair of full 6s should be 12.75ish, so that is why people are saying your batts are not fully charged with the 12.4ish reading.

Does my 6v have a bad internal connection? | Good Sam Community

mchero
Explorer
May 16, 2019
Can you give us more detail on your solar?
wopachop
Explorer
May 16, 2019
Ah man thank you so much. If you are trying to look up the charger to show me it sucks then i would say thanks again but dont waste anymore time.

The batteries in this thread will be installed on a toyhauler soon that has solar and is also plugged into shorepower most of the time.

You guys want to shift gears and give me advice on what solar controller to buy? The controller that came with my trailer is not the best. So im waiting to install my new 6v batteries.

I have that wyco converter.......something like that. Its the converter everyone says is not so great. I want to buy a nice solar controller and maintain my batteries with that.
mchero
Explorer
May 16, 2019
Can't find it on their web site. Can you provide a link?
wopachop
Explorer
May 15, 2019
Its the red harbor freight unit with 2a and 10a charge rates.

I tested 2a and its actually 5a. Just a friendly heads up. I use to charge my tiny motorcycle battery with it sometimes but stopped because 5a is too high. Freakin HF man!!
mchero
Explorer
May 15, 2019
What is the make/model of your battery charger?

You need to get the proper battery charging specs for your batteries and then try and determine if that H.F. charger will properly charge your batteries.

My Xantrex Freedom charging configuration for wet cell batteries will NOT fully charge my four Interstate batteries. I checked them with a battery hydrometer after the Xantrex went to float. Not fully charged!

Got the proper charge specs from Interstate and punched them into my charge controller and now my batteries show charged using hydrometer.
The main issue was the adsorb voltage, not high enough on the Xantrex!

If I had a $ for every RV that was improperly charging their house batteries id be driving around in a Tesla!
MEXICOWANDERER
Explorer
May 15, 2019
Trojan or Rolls battery manuals are FREE downloads. Lifeline has a free PDF download.

Smart chargers may or may not have downloads or paper instructions. But all automatic charger manuals are KEVORKIAN assisted suicide approved.

Something like eating Chinese candy and getting a year's maximum of lead in four pieces.
BFL13
Explorer II
May 15, 2019
Pretend your 6s are Trojans (actually they probably are!) and follow this guide for charging profile

https://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf
wopachop
Explorer
May 15, 2019
This is how the harbor freight charger did on 10a mode. I verified the voltage a few times during this. The battery monitor, multimeter, and inline watt meter all showed the same voltage now that i learned about the threaded post mistake.

Had the charger set to Standard. Dont i want to see close to 14.8v?
MEXICOWANDERER
Explorer
May 15, 2019
On a 5% antimony battery it is normal to see a misleading drop in voltage. By tenths as voltage drops it gets progressively much harder amps per volts. AGM performance is much different. (With a mere 500 watt load my battery bank drops .7 volt)
wopachop
Explorer
May 15, 2019
The graph is not accurate because i had the voltage monitor attached to the threaded posts. The voltage will be accurate while resting. But when i applied the 4a load to the threaded post the voltage dropped to 12.1v. When really the actual voltage was 12.4v.

I guess its just the resistance of that thread. My buddy was saying its because its a different metal.

Shouldnt i be able to measure the resistance between the top of the threads and the flat lead section? Will try that later.

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Does my 6v have a bad internal connection?

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